Abstract
PURPOSE: MRI-based cell tracking identifies the location of magnetically labeled cells with hypointense voxels. Here we demonstrate a strain-dependent effect of liver MRI background on the feasibility of MRI-based cell tracking of transplanted cells in the mouse liver. METHODS: FVB mice (GFP-LUC and NOG) and C57BL/6 mice (GFP+ and wild-type) were fed 3 different diets with varying iron content. In vivo T2∗ -weighted images and T2∗ maps of the liver were acquired at different ages. Magnetically labeled cancer cells were injected intrasplenically for hepatic migration; then, mice were imaged by in vivo MRI and bioluminescence imaging. Livers were also imaged ex vivo by magnetic particle imaging. RESULTS: R2∗ increased with age in FVB(NOG) and FVB(GFP-LUC) mice that were fed diets sufficient in iron. FVB(NOG) mice developed a mottled appearance in their livers with age that did not occur in FVB(GFP-LUC) mice. R2∗ was unchanging with age in C57BL/6(GFP) mice, and the liver remained bright and homogenous. Labeled cells were not detectable by MRI in some livers despite successful engraftment as shown by bioluminescence imaging and magnetic particle imaging. CONCLUSION: Strain, diet, and age are important considerations for MRI-based cell tracking in the liver. If a model with excessive liver iron must be used, alternative imaging methods such as magnetic particle imaging can be considered.